Networked virtual environments allow users at remote locations to use a telecommunication link to coordinate work and social interaction. Teleconferencing systems and virtual environments that use 3D computer graphic displays and digital video recording systems allow remote users to interact with each other, to view virtual work objects such as text, engineering models, medical models, play environments and other forms of digital data, and to view each other's physical environment.
A number of teleconferencing technologies support collaborative virtual environments which allow interaction between individuals in local and remote sites. For example, video-teleconferencing systems use simple video screens and wide screen displays to allow interaction between individuals in local and remote sites. However, wide screen displays are disadvantageous because virtual 3D objects presented on the screen are not blended into the environment of the room of the users. In such an environment, local users cannot have a virtual object between them. This problem applies to representation of remote users as well. The location of the remote participants cannot be anywhere in the room or the space around the user, but is restricted to the screen.
Head-mounted displays (HMDs) have been widely used for 3D visualization tasks such as surgical planning, medical training, or engineering design. The main issues of the conventional eyepiece-based HMD technology include tradeoffs between resolution and field-of-view (FOV), and between compactness and eye clearance, the presence of large distortion for wide FOV designs, the conflict of accommodation and convergence, the occlusion contradiction between virtual and real objects, the challenge of highly precise registration, and often the brightness conflict with bright background illumination. The concept of head-mounted projection displays (HMPDs) is an emerging technology that can be thought to lie on the boundary of conventional HMDs, and projection displays such as the CAVE technology.
After the initial proof of concept using off-the-shelf components, a first-generation custom-designed HMPD prototype was built to investigate perception issues and quantify some of the properties and behaviors of the retro-reflective materials in imaging systems. The projection system of the first-generation prototype was custom designed using a double-Gauss lens structure and built from commercially available components. The total weight of each lens assembly was approximately 50 grams (already a significant reduction compared to using off-the-shelf optics) with mechanical dimensions of 35 mm in length by 43 mm in diameter.
Consequently, there is a need for a HMPD augmented reality display that mitigates the above mentioned disadvantages (in part by an internally mounted projected display that provides visible spectrum images without smears and of reduced weight) and has the capability to display virtual objects and environments, superimposes virtual objects on the “real world” scenes, provides “face-to-face” recording and display, be used in various ambient lighting environments, and corrects for optical distortion, while minimizing weight, computational power and time.
Useful lens assemblies of reduced weight and/or increased field of view (FOV) are taught in co-pending U.S. patent application Ser. No. 10/090,070, filed Mar. 1, 2002, now U.S. Pat. No. 6,731,434, which is incorporated by reference, of common assignee with the instant application. The double-Gauss lens disclosed therein has a FOV of approximately 52 degrees with an effective focal length of approximately 35 mm. Co-pending U.S. patent application Ser. No. 10/418,623, filed Apr. 18, 2003, which is incorporated by reference, of common assignee also with the instant application, discloses a compact lens assembly useful for HMPD systems of miniature display of 0.6″ diagonal with a FOV of approximately 42 degrees and an effective focal length of approximately 17 mm.
Lightweight, compactness, enhanced mobility and improved fidelity of the field of view are always of basic importance and/or highly desirable, particularly, for head-mounted devices and for these reasons the quest for useful compact and lightweight continues. A key to novel solutions in compact light weight HMDs is to pre-magnify, within a very compact space, the microdisplay in the HMD before it is further imaged toward the eyes. Such an approach is the subject of the current invention. However, the ultra-compact magnifier is broadly applicable to all imaging applications where such magnification is required. Such applications include, but are not limited to, imaging systems that perform magnified-relaying (i.e. magnification greater than 1), demagnified-relaying (i.e. magnification is less than one), or relaying (i.e. magnification equal to one). Examples of such imaging systems include, but are not limited to, images in scanners, copiers, cameras, microscopes, projection systems, eyepieces, and telescopes,